Particularly in the plumbing and waterworks industries, situations frequently arise where it is important to ensure that a fluid flows through a conduit in only one direction. Such a result is often achieved by introducing a check valve into the conduit. Check valves utilize any of a variety of valve mechanisms, including balls, flaps, swing doors, and poppets to allow fluids to flow in one direction, but not the other.
One exemplary situation in which uni-directional flow is desirable is in residential water supply applications. In such applications, it is preferable to allow water to flow only from the water main into the residence, and not vice versa. This is because should water flow from the residence to the water main (which can occur when there is a pressure drop in the water main caused by, for example, a broken water main or burst fire hydrant), the municipal water supply can be contaminated. Traditionally, residential water supply applications have not included check valves. However, in view of increasing concerns about the safety of municipal water supplies, a demand has arisen among municipalities to retrofit existing residential water supply plumbing to install check valves therein.
Many existing check valves however have been found to be unsuitable for use in such retrofits for various reasons. For example, many existing check valves are simply too long or are otherwise too large to fit in the available space. Others utilize valve mechanisms which do not allow for sufficient flow rates thereby unacceptably reducing residential water pressure. Other valves have too many moving parts or parts which can fall out of the valves during handling, resulting in difficulties during installation. Finally, many check valves are simply not suitable for situations where neither of the connections between which the valve is to be mounted, is rotatable, as may be the case when inserting a check valve between a water meter and a supply line in a retrofitting application.
Poppet-style valves are particularly advantageous for such applications because they tend to be simple, durable, reliable and compact. Typically, poppet-style valves consist of one or more sealed valve units contained within a sleeve. Such valve units have a first and a second end and include a poppet, a disk having a guidepost extending perpendicularly from its center, reciprocally slidable axially within the valve unit. The poppet has a sealing surface which can seat against an annular surface at the first end of the valve unit. The poppet is biased towards the first end such that its sealing surface seats against the annular surface when no flow exists through the valve unit. When the fluid pressure at the second end of the valve unit is greater than that at the first end, this pressure differential tends to hold the poppet tightly against the annular surface thereby increasing the sealing force. When the fluid pressure at the first end exceeds the fluid pressure at the second end by an amount sufficient to overcome the biasing of the poppet towards the annular surface, the poppet moves away from the annular surface allowing for fluid flow through the valve unit from the first end to the second end. The sleeve has connections at either end to allow the valve to be mounted in-line in a conduit.
Despite its advantages, poppet-style valves have only seen limited use in residential water supply retrofit applications. This is because conventional designs result in valves having limited flow rates, valves which are often too large for retrofitting applications, and valves which are difficult to service in the field.